One of the most important themes in this excellent novel is the past and memory and our relation with it in the present. The novel presents us with a man who is haunted by something that happened in his childhood, and that he has been doing his best to forget--unsuccessfully--ever since. A quotation that introduces this theme to the reader is in Chapter 1:

That was a long time ago, but it’s wrong what they say about the past, I’ve learned, about how you can bury it. Because the past claws its way out. Looking back now, I realize I have been peeking into that deserted alley for the last twenty-six years.

Later, the reader discovers exactly what happened in that "deserted alley" Amir refers to, and how Amir's decision to not act whilst Hassan was raped by Assef leaves Amir scarred for life because of his inaction and his choice to stand by and do nothing. The whole novel in a sense is about the way that characters cannot escape their past and have to face up to their past actions at some point in the future. It is this process of how Amir faces up to his past and resolves his guilt that occupies the majority of the novel, and moves him towards redemption for his past mistakes and errors. This quote is therefore important because it introduces not only one of the central themes of the novel but the main action of the novel, as the past is replayed for the reader and then "claws its way out" into Amir's life in his present, forcing him to face up to his past actions.